u, Ka

Bond properties

usixurwit wtrenughresth

(LWACction.or thers, andages oessivethe wrmal c

trial processes, are man-made lightweight aggregates. The maincharacteristic of lightweight aggregate is its high porosity, whichresults in a low specic gravity. Although commercially availablelightweight aggregate has been used widely for manufacture ofLWC, more environmental and economical benets can beachieved if waste materials can be used as lightweight aggregatesin concrete. In view of the escalating environmental problems, theuse of aggregates from by-products and/or solid waste materials

weight aggregates is an interesting topic for further studies. Thiscoconut shell can be crushed and used as a coarse aggregate inthe production of LWC. Coconut Shell Concrete (CSC) could be usedin rural areas and places where coconut is abundant and may alsobe used where the conventional aggregates are costly. In this study,the important mechanical properties of CSC, namely compressive,exural, splitting tensile strengths and impact resistance havebeen measured to assess its suitability as a lightweight aggregate.The bonding property of CS is also studied to analyze the suitabilityfrom a structural point of view. The results are produced in the fol-lowing paragraphs.

* Corresponding author. Tel.: +91 9443353507; fax: +91 44 27453903.

Construction and Building Materials 25 (2011) 9298

Contents lists availab

B

evE-mail address: gunarishi@yahoo.com (K. Gunasekaran).2535% lighter [2]. Structural LWC offers design exibility andcost savings due to self-weight reduction, improved seismic struc-tural response, and lower foundation costs. Lightweight concretepre-cast elements offer reduced transportation and placementcosts [3].

Pumice, scoria and other materials of volcanic origin are thelightweight aggregates available naturally. Expanded blast-furnaceslag, vermiculite and clinker, which are the by-products of indus-

and annual production of 2.74 million tones copra equivalent [8].Within India, 90% of the total production of coconut is concen-trated in South India (www.foodmarketexchange.com). The aver-age annual production of coconut is estimated at about 15 billionnuts in India (www.cpcri.ernet.in). After the coconut is scrapedout, the shell is usually discarded as waste. The vast amount of thisdiscarded CS resource is yet unutilized commercially; its use as abuilding material, especially in concrete, on the lines of other light-1. Introduction

Lightweight aggregate concreteversatile material in modern construdue to its lower density and superities [1]. Many architects, engineerthe inherent economies and advantas evidenced by the many impr(LWC) structures found throughoutcrete has strengths comparable to no0950-0618/$ - see front matter 2010 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2010.06.053) is an important andIt has gained popularitymal insulation proper-contractors recognize

ffered by this material,lightweight concreteorld. Lightweight con-oncrete; yet is typically

from different industries is highly desirable. In recent years,researchers have also paid more attention to some agriculturewastes for use as building material in construction [47]. One suchalternative is coconut shell (CS), which is one of the most commonagricultural solid wastes in many tropical countries [6].

The main coconut players in the global market for 2005 areshown in Table 1. Eight of the ten largest producers are in the AsiaPacic region. The three main producers, Indonesia, the Philippinesand India account for 75% of world production. India is the thirdlargest coconut producing country, with an area of 1.9 million haMechanical and bond properties of cocon

K. Gunasekaran *, P.S. Kumar, M. LakshmipathyDepartment of Civil Engineering, Faculty of Engineering and Technology, SRM University

a r t i c l e i n f o

Article history:Received 29 November 2009Received in revised form 12 May 2010Accepted 19 June 2010

Keywords:Coconut shellAggregateLightweight concreteMechanical

a b s t r a c t

The properties of concretetal study. Compressive, emeasured and comparedselected mix, two differenural and splitting tensile sties were determined throlightweight concrete. Thecrete is much higher thanselected.

Construction and

journal homepage: www.elsll rights reserved.t shell concrete

ttankulathur 603 203, TamilNadu, India

ng coconut shell as coarse aggregate were investigated in an experimen-al, splitting tensile strengths, impact resistance and bond strength wereth the theoretical values as recommended by the standards. For theatercement ratios have been considered to study the effect on the ex-gths and impact resistance of coconut shell concrete. The bond proper-pull-out test. Coconut shell concrete can be classied under structural

ults showed that the experimental bond strength of coconut shell con-e bond strength as estimated by BS 8110 and IS 456:2000 for the mix

2010 Elsevier Ltd. All rights reserved.

le at ScienceDirect

uilding Materials

ier .com/locate /conbui ldmat

versity specically for this purpose. The crushed edges were rough

lar river bed) was used throughout the investigation as the ne

0.44 was considered to study the exural and splitting tensilestrengths and impact resistance of CSC. The bond strength betweenthe concrete matrix and the steel reinforcement is one of the mostimportant aspects in structural reinforced concrete. A perfect bondexisting between concrete and steel reinforcement is one of thefundamental assumptions of reinforced concrete [9]. Therefore,an investigation was carried out by conducting pull-out test onboth plain and deformed steel bars to determine the bond strengthof CSC.

3.1. Studies on cement content

It has been reported that the cement content for LWC lies be-3

Table 1Selected coconut production statistics, 2005.

Country Production (nuts) Area

(kt) (%) (ha) (%)

Indonesia 16,300 30.1 2670 25.0Philippines 14,797 27.3 3243 30.4India 9500 17.5 1860 17.4Brazil 3034 5.6 281 2.6Thailand 1500 2.8 343 3.2Vietnam 972 1.8 110 1.0Mexico 950 1.8 150 1.4Sri Lanka 890 1.6 395 3.7Papua New Guinea 650 1.2 180 1.7Malaysia 642 1.2 179 1.7

K. Gunasekaran et al. / Construction and Building Materials 25 (2011) 9298 93aggregate conforming to grading zone III as per IS 383:1970. Thepotable water from the University was used for mixing and curing.Specimens were cast in such a way as to produce full compactionof the concrete with neither segregation nor excessive laitance.Compaction was achieved through use of a table vibrator.

3. Experiments

Table 3 shows the set of experiments and number of samplesused for measuring the mechanical and bond properties of CSC.The studies on the effect of cement content and woodcement ra-tio on CSC included the effect of watercement ratio on the work-ability by measuring slump, densities and compressive strength.and spiky and the lengths were restricted to a maximum of 12 mm.The surface texture of the shell was fairly smooth on concave andrough on convex faces. CS aggregates used were in saturated sur-face dry (SSD) condition. The physical properties of CS were com-pared with crushed granite and oil palm shell (Table 2).

2.2. Other concrete mix constituents

Ordinary Portland Cement (OPC) 53 Grade conforming to IndianStandard IS 12269:1987 was used as a binder. River sand (from Pa-2. Materials used

2.1. Coconut shell as coarse aggregate

The freshly discarded shells were collected from the local oilmills and they were well seasoned. The seasoned CS is crushedby a mini crusher, which was developed and erected in SRM Uni-For one mix, the effect of free watercement ratios of 0.42 and

Table 2Properties of coconut shell, oil palm shell, crushed granite and river sand.

Sl. No Physical and mechanical properties Coconut shells

1 Maximum size (mm) 12.52 Moisture content (%) 4.203 Water absorption (24 h) (%) 24.004 Specic gravity 1.051.20

SSDa apparent 1.401.505 Impact value (%) 8.156 Crushing value (%) 2.587 Abrasion value (%) 1.638 Bulk density (kg/m3) 650

Compacted loose 5509 Fineness modulus 6.26

10 Shell thickness (mm) 28

a Saturated surface drytween 285 and 510 kg/m [5]. It was proposed to achieve the targetto produce structural concrete with CS as a coarse aggregate. Anumber of trial mixes were made using weigh batches with differ-ent cement contents varying from 300 to 510 kg/m3 and by adjust-ing ne aggregate and coarse aggregate (coconut shell) ratios toreach the target. Watercement ratio varied between 0.42(510 kg/m3) and 0.72 (300 kg/m3). From the 33 trial mixes pre-pared, 11 mixes were selected, designated as M1 M11. The prop-erties of the 11 mixes at 28 days are presented in Table 4.

3.2. Studies on woodcement ratio

Literature shows that the woodcement composites need en-ough cement to fully encapsulate wood materials to get a cohesivemix with acceptable properties [10]. A lower woodcement ratiowill result in weak bonds. However, if the amount of cement istoo high, the compaction ratio will be reduced, leading to a brittlematerial. So woodcement ratio strongly inuences the propertiesof the nal product. A woodcement ratio below 0.5 had an ad-verse effect on strength of cement concrete composites [11].Hence, it is necessary to optimize the woodcement ratio andwatercement ratio for coconut shell aggregate concrete. For opti-mization of the woodcement ratio to achieve the target strengths,the cement content of the CSC samples was set at 510 kg/m3 as se-lected from the trial mix. Woodcement ratios of 0.55, 0.60 and0.65 have been considered for this study and ne aggregate ratioswere also adjusted appropriately. From the 27 trial mixes pre-pared, 9 mixes were selected. These are designated as CS1 CS9and their properties at 28 days are given in Table 5.

3.3. Studies on watercement ratio

It is not easy to specify an optimal watercement ratio for allkinds of woodcement concrete composites, since the propertiesof woodcement composites are varying in nature [12]. It has beenfound that with the increase of watercement ratio, the strength of

Oil palm shells [4,5,19] Crushed granite River sand

12.5 12.5 23.32 0.50 1.17 2.82 2.57 2.86 7.86 12.40 6.30 4.80 1.85 590 1650 1450 6.24 6.94 2.56

1.52.5

Age during test

cubes in each trial, total of 297 cubes 3-days, 7-days and 28-dayscubes in each trial, total of 243 cubes 3-days, 7-days and 28-dayseams in each trial, total of 6 beams 28-daysylindpecipeci

ne

nd Building Materials 25 (2011) 9298Table 3Experimental programme to assess mechanical and bond properties of CSC.

Sl. No Parameter No. of trials

1 To meet structural concrete criteria 33 trials, 92 To optimize the woodcement ratio 27 trials, 93 Flexural strength 2 trials, 3 b4 Splitting tensile strength 2 trials, 3 c5 Impact strength 2 trials, 3 s6 Bond properties 8 trials, 3 s

Table 4Properties of selected trial mixes of CSC at 28-days.

Sl. No Cement content (kg/m3) Watercement ratio Mix ratio (cement:

94 K. Gunasekaran et al. / Construction athe woodcement concrete composites gets reduced. In this study,watercement ratios of 0.38, 0.42 and 0.48 have been considered.

3.4. Mechanical properties

The compressive strength of 100 mm cubes was measuredaccording to IS 516:1959 [13]. Mix CS8 (1:1.47:0.65:0.42) was usedto study the exural, splitting tensile strengths and impact resis-tance of CSC. Also, watercement ratio was increased by 0.02 tostudy its inuence. The 28-days exural and splitting tensilestrengths and impact resistance of CSC for the selected mix are gi-ven in Tables 6 and 7.

3.4.1. Flexural strength testFour-point load method was adopted to measure the exural

strength of CSC. As per ASTM guidelines [14], beams of

aggregate: CS)

M1 300 0.72 1:3.27:1.34M2 400 0.55 1:2.05:0.84M3 425 0.50 1:1.93:0.79M4 450 0.45 1:1.83:0.75M5 480 0.51 1:1.37:0.75M6 480 0.42 1:1.67:0.69M7 480 0.42 1:1.52:0.75M8 480 0.44 1:1.60:0.80M9 480 0.42 1:1.60:0.80M10 480 0.42 1:1.60:0.70M11 510 0.42 1:1.47:0.65

Table 5Properties of CSC with at 28-days optimized woodcement ratio (cement content 510 kg/

Sl. No Woodcement ratio Watercement ratio Mix ratio (cement:neaggregate:CS)

CS1 0.55 0.38 1:1.82:0.55CS2 0.55 0.42 1:1.74:0.55CS3 0.55 0.48 1:1.57:0.55CS4 0.60 0.38 1:1.70:0.60CS5 0.60 0.42 1:1.60:0.60CS6 0.60 0.48 1:1.44:0.60CS7 0.65 0.38 1:1.58:0.65CS8 0.65 0.42 1:1.47:0.65CS9 0.65 0.48 1:1.32:0.65

Table 6Flexural and splitting tensile strengths of CSC at 28-days.

Mix ratio (cement:neaggregate:CS:watercement)

Compressivestrength (N/mm2)

Flexuralstrength (N/mm2)

Split tensilestrength (N/mm2)

1:1.47:0.65:0.42 26.70 4.68 2.701:1.47:0.65:0.44 25.95 4.26 2.38ers in each trial, total of 6 cylinders 28-daysmen in each trial, total of 6 specimen 28-daysmen in each trial, total of 24 specimen 28-days

Slump (mm) Hardened density (kg/m3) Compressive strength (N/mm2)

10 1865 04.9525 1890 09.8115 1910 13.2425 1960 13.49

110 1900 10.3065 1990 15.2050 1950 16.1950 1910 16.6805 1930 17.66100 100 500 mm size as shown in Fig. 1 were adopted. Theload was applied without shock and was increased until the spec-imen failed, and the maximum load applied to the specimen duringthe test was recorded. The appearances of the fractured faces ofconcrete failure were noted. The exural strength of the specimenswas calculated as follows:

Modulus of rupture; f b PL=bd2; 1where P = Maximum load applied (N). L = Supported length of thespecimen (mm). b = Measured width of the specimen, mm. d = Mea-sured width of the specimen at the point of failure (mm).

3.4.2. Splitting tensile strength testAs per ASTM guidelines [15], 100 mm diameter 200 mm long

cylinders were used for splitting tensile strength test (Fig. 2). The

30 1980 18.1505 1970 26.70

Table 7Impact resistance of CSC at 28-days.

Mix ratio(cement:neaggregate:CS:watercement)

Compressivestrength (N/mm2)

Average numberof blows forinitial crack

Average numberof blows forfractured pieces

1:1.47:0.65:0.42 26.70 25 321:1.47:0.65:0.44 25.95 17 23

m3).

Slump (mm) Hardened density (kg/m3) Compressive strength (N/mm2)

00 2060 23.4005 2040 16.72

140 1960 13.3800 2010 19.5000 1990 16.1640 1980 13.3800 1985 27.2005 1970 26.70

150 1920 14.50

test specimen was placed in the centering jig with packing stripand/or loading pieces carefully positioned along diametrically ver-tical planes at the top and bottom of the specimen. The maximumdiametrical load applied was recorded. The measured splitting ten-

sile strength fsp of the specimen was calculated using the followingformula:

fsp 2P=pDL 2where P = maximum load applied to the specimen (N). D = crosssectional diameter of the specimen (mm) and L = length of the spec-imen (mm).

3.4.3. Impact resistanceThe method developed by ACI committee 544.1R-82 for the

determination of impact resistance of concrete was adopted.The test specimens used for the impact tests were 152.4 mmin diameter and 63.5 mm thick. The test equipment with thespecimen is shown in Fig. 3 (as recommended by the ACICommittee 16-81). During this test, the number of blows

Table 8Bond strength of CSC with plain bars (mix ratio 1:1.47:0.65:0.42).

Diameter ofbar (mm)

Experimental bondstress (N/mm2)

Theoretical bond stress (N/mm2)

IS: 456-2000 BS: 8110

8 7.4910 6.5412 4.99 1.40 1.3616 3.56

Fig. 1. Flexural test on CSC. (a) Flexural test specimen in UTM and (b) tested specimen of exural test.

ne (C

K. Gunasekaran et al. / Construction and Building Materials 25 (2011) 9298 95Fig. 2. Splitting tensile test on CSC. (a) Splitting testing in compression testing machisplit tensile.Fig. 3. Impact resistance test on CSC. (a) Impact resistance testing instrument. (b) TTM) and (b) tested specimen of split tensile in CTM and Fig. 3 (c) tested specimen ofesting of specimen under impact and (c) tested specimen of impact resistance.

was counted till the rst crack appeared (initial crack) on eachspecimen and counting was continued till the specimen wasbroken into a number of pieces. The results are presented inTable 7.

3.5. Bond properties

The bond strength was determined using the pull-out test andthe specimens were prepared as per IS 2770 (part-I 1967) [16].

Fig. 4. Pull-out test on CSC in UTM. (a) Bond (pull-out) testing in UTM. (b) Closure view of specially fabricated steel plates attached with UTM to conduct pull-out test.

96 K. Gunasekaran et al. / Construction and Building Materials 25 (2011) 9298Fig. 5. Schematic diagram of attachment made with UTM. Representing a schematic diaout) test.gram of specially fabricated steel plates attached to the UTM to conduct bond (pull-

The specimens were of 100 mm diameter and 200 mm heightincorporating both deformed and plain bars of 8, 10, 12 and16 mm diameters. For each specimen, a single reinforcing barwas placed in the centre and both ends were provided with anun-bonded length of 25 mm. The un-bonded lengths were pro-vided by attaching a plastic sheathing to the bar. A short embed-ment length of 150 mm was selected to avoid yielding of the

2

imum 28-days compressive strength should be greater than 17 N/2

K. Gunasekaran et al. / Construction andmm . This criterion is satised for the CSC mixes M9, M10 and M11(Table 4). The cement content required to meet this minimumrequirement lies between 480 kg/m3 and 510 kg/m3. This resultalso conforms to published literature [5].

4.2. Woodcement ratio

Referring to Table 5, a woodcement ratio of 0.65 may be takenas optimum for CS aggregate to satisfy the criteria of structuralLWC strength as per ASTM [18].

4.3. Workability and density

The results for workability and density are presented in Tables 4and 5. Coconut shell concrete probably has better workability dueto the smooth surface on one side of the shells and also due to thesmaller size of CS used in this study. This same trend was also re-ported by Basri [19]. For typical trial mixes, the 28-days air-drydensities of CSC are less than 2000 kg/m3 and these are withinthe range of structural LWC [7].

Table 9Bond strength of CSC with deformed bars (mix ratio 1:1.47:0.65:0.42).

Diameter ofbar (mm)

Experimental bondstress (N/mm2)

Theoretical bond stress (N/mm2)

IS: 456-2000 BS: 8110

8 9.8410 7.45where i is the bond stress (N/mm ), F the applied load (N), d thenominal bar diameter (mm) and l the embedment length (mm).The results of the pull-out test are given in Table 8 and Table 9for plain bars and deformed bars, respectively.

4. Discussions on test results

4.1. Cement content

To satisfy the criteria of structural LWC as per ASTM [18], min-specimen until failure to obtain the ultimate load [17]. The bondstrength is reported as an average of three tests in each case. Theexperimental bond strength was computed using the followingformula:

i F=p d l 3steel bar under pull-out load. To prevent excessive evaporationfrom the fresh concrete, the specimens were immediately coveredwith plastic sheets upon casting and then de-molded after 24 h.The pull-out test was carried out using the Universal Testing Ma-chine (UTM) of 400 kN capacity. In order to pull the steel rod fromthe specimen, a special attachment was made with steel plates andused, as shown in Fig. 4. A schematic diagram of the attachmentalong with the UTM is shown in Fig. 5. One end of the rod was t-ted with grips provided in the machine, which is movable in verti-cal, and load was applied by pulling the rod upward from the12 5.93 2.24 2.4216 4.224.4. Compressive strength

Compressive strength of LWAC depends on both the strength ofthe matrix and the particle tensile strength of the aggregate. Again,the compressive strength of LWC is usually related to the cementcontent at a given slump and air content, rather than to waterce-ment ratio. This is due to the difculty in determining howmuch ofthe total mix water is absorbed by the aggregate and is thus notavailable for reaction with the cement [20]. However, in this study,CS coarse aggregates were used in SSD condition and the waterce-ment ratio was optimized to obtain desired workability. The com-pressive strengths of the CSC cube samples for all the trials areshown in Tables 4 and 5. An examination of the failure surfacesshowed breakage of the CS aggregate, indicating that the individualshell strength had a strong inuence on the resultant concretestrength.

4.5. Flexural strength

The exural strength of CSC at 28-days is presented in Table 6.For the selected mixes, the exural strength is 4.68 N/mm2 (17.53%of compressive strength) and 4.26 N/mm2 (16.42% of compressivestrength), respectively, for watercement ratios of 0.42 and 0.44.For conventional concrete, the exural strength is usually 1015% of compressive strength. Compared to the exural strengthas per IS 456:2000 [21], 0.7

pfck, where fck is the compressive

strength of conventional concrete, these values are higher by 29%and 19%, respectively. It reinforces the assumption that the behav-ior of CSC would be similar to that of conventional concrete. In con-crete with conventional aggregates, the failure in tension occurs asa result of breaking of bond between the matrix and the surface ofthe aggregate used or by fracture of the concrete matrix itself. Eventhough CS is liable to fracture unlike the conventional aggregates,this did not occur in any of the experiments when it is used asaggregate. This shows that the brittle nature of CS is not a limitingfactor for its use as aggregate. When the size of the shells is re-duced, the ability to be fractured easily also probably decreases.This shows that the behavior of CSC is also similar to that of con-ventional concrete. However, further research is required on CSCto establish the co-efcient to be used to nd out the exuralstrength from the compressive strength. Compressive strengthand exural strength depend to some extent on the physicalstrength of conventional aggregates. They are also inuenced bythe watercement ratio in the samples [22]. This holds true forCS also as evidenced by this study.

4.6. Splitting tensile strength

The splitting tensile strength of CSC at 28-days is presented inTable 6. For the selected mixes, the splitting tensile strength is2.70 N/mm2 (10.11% of compressive strength) and 2.38 N/mm2

(9.17% of compressive strength), respectively, for watercementratios of 0.42 and 0.44. Hence, it is evident that the behavior ofCSC is similar to conventional concrete. A similar result is also re-ported for oil palm shell concrete [4].

4.7. Impact resistance

The impact resistance generally increased with concretestrength both for initial crack and for failure (Table 7). However,in normal concrete there appears to be an optimum value beyondwhich any increase in strength reduces the impact resistance bothat rst crack and at failure [23]. Literature shows that the number

Building Materials 25 (2011) 9298 97of blows required for the failure of normal aggregate concrete hav-ing compressive strength of around 45 N/mm2 is in the range of1022 [23], but in this study, for CSC having compressive strengths

of 25.95 N/mm2 and 26.70 N/mm2, 2332 blows were required,nearly 50% more. This increase may be due to the brous natureof the CS aggregate and its high impact resistance.

are under way to assess its durability and suitability in structuralapplications.

98 K. Gunasekaran et al. / Construction and Building Materials 25 (2011) 92984.8. Bond strength

The theoretical bond strengths were obtained using the formulaas per BS 8110 [24]:

fbu bf

pcu 4

where fbu is the theoretical bond strength (N/mm2); b the bondcoefcient (0.28 for MS bars and 0.50 for RTS bars) and fcu the com-pressive strength of concrete (N/mm2). The bond strength of speci-mens with plain bars ranged from 3.56 to 7.49 N/mm2 (1532% ofcompressive strength). For deformed bars, the bond strength rangedfrom 4.22 to 9.84 N/mm2 (1842% of compressive strength). Thetheoretical bond strengths for plain bars in conventional concreteare 1.4 and 1.36 N/mm2 as per IS 456-2000 and BS 8110, respec-tively. The corresponding values for deformed bars are 2.24 and2.42 N/mm2. In general, the bond strength of CSC is comparableto the bond strength of normal and other LWC. Similar trends werereported by Teo et al. [25].

In all the tests, plain bars failed by pulling out of the concretewhereas, deformed bars failed by concrete cover cracking and thefailure was sudden with the formation of longitudinal cracks. Thedeformed bars had a good grip on the concrete through well-dis-tributed mechanical anchorages along their length. This showedthat the projections on the surface of the deformed bars playedan important role in improving the bond strength. In case of plainbars, the absence of anchorages and smooth surface on one side ofthe CS aggregates coupled with the continuous presence of watermight have prevented good bond between the smooth bars, whichcontributed to the lower bond strength as compared with de-formed bars. However, even this lower bond strength value forplain bars is greater than the theoretical prediction as per stan-dards. It was also observed that for both plain and deformed bars,as the bar size increases, the bond strength decreases. This may bebecause the surrounding volume of concrete and hence the conn-ing pressure reduces on the reinforcing bar as the sizes increase.

5. Conclusions

Coconut shell concrete has better workability because of thesmooth surface on one side of the shells and the size of CS usedin this study. The 28-days air-dry densities of CS concrete of thetypical mixes ranged from 1930 to 1970 kg/m3 and these are with-in the range of structural lightweight concrete of density less than2000 kg/m3 [7]. The exural strength of CSC is approximately17.53% and 16.42% of its respective compressive strengths(26.70 N/mm2 and 25.95 N/mm2). The splitting tensile strength ofCSC is approximately 10.11% and 9.17% of its respective compres-sive strengths. The impact resistance of coconut shell aggregateconcrete is high when compared with conventional concrete. Theexperimental bond strength of CSC is much higher compared tothe theoretical bond strength as stipulated by IS 456:2000 andBS 8110. In general, the bond strength of CSC is comparable tothe bond strength of normal and other lightweight aggregate con-cretes. The experiments prove that coconut shells fulll therequirements for use as lightweight aggregate. Further studiesAcknowledgements

This project is funded by SRM University, Kattankulathur, India,under Pilot Research Project Scheme (PRPS) 20082009. Theauthors wish to thank the SRM management, for their nancialaid as well as the technical support and those who were directlyor indirectly involved in this study.

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[13] IS: 516-1959. Methods of tests for strength of concrete, edition 1.2 (1991.-07).[14] ASTM C78-84. Standard test method for exural strength of concrete. Annual

Book of ASTM Standards.[15] ASTM C496-90. Standard test method for splitting tensile strength of

cylindrical concrete specimens. Annual Book of ASTM Standards.[16] IS: 2770-(Part I)-1967. Indian standard methods of testing bond in reinforced

concrete. UDC 666.982: 620.172.21.[17] ASTM C234. Standard test method for comparing concrete on the basis of bond

development with reinforcing steel. Annual Book of ASTM Standards.[18] ASTM C330. Standard specication for lightweight aggregates for structural

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1999;29:61922.[20] Grubl P. Mix design of lightweight aggregate concrete for structural purposes.

Lightweight Concr 1979;1(2):639.[21] IS 456: 2000. Indian standard plain and reinforced concrete code of practice,

BIS, New Delhi; 2000.[22] Short A, Kinniburgh W. Lightweight concrete. 3rd ed. London: Applied Science

Publishers.; 1978.[23] Swamy RN, Jojagha AH. Impact resistance of steel bre reinforced lightweight

concrete. Cem Compo Lightweight Conc 1982;4(4):20920.[24] BS 8110. Structural use of concrete Part 1. Code of practice for design and

construction. London: British Standard Institution.[25] Teo DCL, Mannan MA, Kurian VJ, Ganapathy C. Lightweight concrete

made from oil palm shell (OPS): structural bond and durability properties.Build Environ 2007;42:261421. 01.05.2010 @8.30pm. #Description on 03.05.2010 at 11.50 am IST.

Mechanical and bond properties of coconut shell concreteIntroductionMaterials usedCoconut shell as coarse aggregateOther concrete mix constituents

ExperimentsStudies on cement contentStudies on woodcement ratioStudies on watercement ratioMechanical propertiesFlexural strength testSplitting tensile strength testImpact resistance

Bond properties

Discussions on test resultsCement contentWoodcement ratioWorkability and densityCompressive strengthFlexural strengthSplitting tensile strengthImpact resistanceBond strength

ConclusionsAcknowledgementsReferences